Exhaust system for internal combustion engines provided with a device for housing filters designed to trap solid particles and unburned hydrocarbons entrained in exhaust gases

ABSTRACT

The exhaust system is suitable for both gasoline and diesel engines, whether used for vehicle propulsion or in permanently installed power transmissions, and controls emission by trapping the solid matter and unburned hydrocarbons that escape with the exhaust gases using serviceable filters accommodated in an elongated hollow outer case (6,61) sealed at either end by removable caps (7) with axial fittings (10) that connect with the front and rear sections of the exhaust pipe (2,4); the space encompassed by the case (6) is split into two chambers (13,14) of different volume by a baffle (15), one side of which supports a housing (16) designed to contain one or more removable filter elements (19), and at the same time, to combine with the inside wall of the case (6) in creating a void (20) that communicates with the smaller chamber (13) by way of openings formed in the baffle (15).

DESCRIPTION

The present invention relates to an exhaust system for internalcombustion engines, whether fuelled by carburation or injection (Ottocycle petrol engines) or by injection and compression-ignition (diesel),and whether used for the propulsion of vehicles, or as prime movers inpermanently-installed domestic, community or industrial power units, andfeatures a device in which to house replaceable filters serving for theabatement essentially of solid particles and unburned hydrocarbonsentrained in exhaust gases.

The basic problem tackled by the invention is one generally associatedwith current research aimed at finding the most effective methods andmeans of eliminating the main polluting agents from exhaust gasesemitted by internal combustion engines.

The polluting agents in question are identifiable in the main as carbondioxide, hydrocarbons that have escaped combustion, oxides of nitrogen,sulphur and lead, and entrained solid matter or fuel ash, which will bepresent in proportions that vary according to the different types ofengine, and attributable for the most part to less-than-perfect minglingof the air-and-fuel mixture, and incomplete combustion. Attempts to curbpollution have been made thus far in two main directions. On the onehand, research has been concentrated on improving and modifying thecarburation, injection and mixing of engine fuels, experimenting withthe shape of combustion chambers, valves and passages, and optimizingthe combustion cycle; on the other, researchers have recognized theextreme difficulty of creating ideal conditions for combustion andmaintaining them constant in the long term, and in the various operatingand environmental situations encountered. Accordingly, efforts have alsobeen made to find ways and means, remote from the engine, of reducingemissions to as great an extent as possible.

To this end, thermal reactors have been designed that induce reheat byinjecting further fuel and air at suitable temperature; a chemical typeof reheat has also been produced by the adoption of catalytic silencers,although these silencers have proven to be effective only against theoxides of carbon and nitrogen and unburned hydrocarbons, whereas rapiddeterioration occurs through poisoning of the noble catalyst metal bylead oxides and entrained matter. Diesel engines, in particular, produceexhaust gases in which the concentration of entrained particles is muchhigher than that of the oxides of nitrogen, and as catalytic silencerscannot be utilized in such a situation, remedies must be sought inimprovement of the combustion cycle and regular servicing of the engine.

Finally, attempts have been made to fit a variety of types of filter tothe tail-pipe, e.g. wire mesh, fabric, foam, dry or oil-bath etc. . .Such expedients have proved totally unsuitable however, by reason of therapid rate at which blockage occurs; a blocked filter occasionsback-pressure through the exhaust system, and as a result, significantloss of engine output and further deterioration of the combustion cycle.

Accordingly, the main object of the invention is one of remedying thelimitations and drawbacks described above by adoption of an exhaustsystem incorporating a rigidly attached or removable device that is ableto accommodate one or more filtered elements, and can be reached fromthe outside for easy inspection and replacement of the spent elementsand/or for general cleaning.

A further object of the invention is to provide a device that isdesigned, structured and installed in such a way as to guarantee maximumfiltration on the part of the filter elements, especially in the case ofsolid particles and unburned hydrocarbons, and at the same time, toensure that performance of the engine remains steady and unaffected evenwith the filters completely spent: in short, that no danger exists ofback-pressure being generated through the exhaust system.

Another object of the invention is to provide a filtration devicesuitable for use with any type of internal combustion engine, but mostespecially with diesels. Diesel engines currently constitute a majorsource of pollution mainly by reason of the notable quantity of fuelash, entrained solids and unburned hydrocarbons emitted with theirexhaust gases; the presence of such substances is a principal factor inincreasing smoke from the exhaust pipe, at present, the one indicator ofa diesel engine's pollution potential that can readily be monitored.

An additional object of the invention is to provide a filtration devicethat can either be fitted with no difficulty to any given point of anexisting exhaust system, or designed permanently or removably into newsystems.

Yet another object of the invention is to provide a filtration devicedesigned and structured in such a way as to permit embodiment of anexhaust silencer capable of supplementing or replacing conventionalexhaust silencers.

The stated objects, and others besides, are realized by adoption of anexhaust system as characterized in the appended claims. The exhaustsystem according to the invention comprises a device that consists in ahollow outer case, enclosed at its ends by removable caps thatincorporate fittings for axial connection to the exhaust pipe, theinside of which is divided by a baffle into two chambers of dissimilarvolume, the larger chamber accommodating a housing, rigidly associatedwith the baffle, in which one or more serviceable filter elements arelodged; the outside of the housing and the inside of the case combine tocreate a passage that communicates with the smaller chamber by way ofopenings in the baffle.

The invention will now be described in detail, by way of example, withthe aid of the accompanying drawings, in which:

FIG. 1 is the schematic representation of a typical conventional exhaustsystem;

FIG. 2 is a longitudinal section through a preferred embodiment of thefiltration device according to the invention;

FIGS. 3a and 3b are each a section through 3a--3a in FIG. 2 in twopossible embodiments;

FIG. 4 is a partially broken longitudinal view of the device shown inFIG. 2, seen partly in longitudinal section, illustrating its operationas an exhaust silencer;

FIG. 5 is a section view taken as in FIG. 3a but of a schematicillustration of a further embodiment of the invention, in which thefiltration device is accessible from the side;

FIGS. 6a and 6b are partial longitudinal views of an additional featureof the invention respectively showing two different methods for theirincorporation into the exhaust system.

With reference first to FIG. 1, of the above drawings, there is anexhaust manifold 1, in its entirety, from which gases expelled by thecombustion chambers of a petrol or diesel engine are directed through afirst pipe 2 into a silencer 3 and out ultimately by way of a secondpipe 4 into the surrounding atmosphere. These single parts make up atypical exhaust system, and are connected one to the next at a number ofpoints, denoted 5 in FIG. 1; a filtration device according to theinvention can be fitted at any one these points 5.

FIG. 2 affords a view of the device in longitudinal section. 6 denotes ahollow outer case with open ends that are sealed tight by twosubstantially identical caps 7 clamped in place rigidly, thoughremovably, by conventional means denoted 8; in the example illustrated,such means 8 consist in a set of fasteners each comprising a tension rod81 with relative sleeves 82 and nuts 83, though other types of removableclamp might equally well be adopted. Each cap 7 affords a opening 9 atcenter, serving to accept a respective fitting 10 by which the device isconnected axially to the manifold 1 and/or to the first pipe 2, thesilencer 3, or the second pipe 4. Each fitting 10 consists essentiallyin a tube 11, integral with a flange 12, that slots through the cap 7and can be rigidly and hermetically fastened to it, the flange 12 beingdistanced from the end of the tube 11 in such a way as to limit thepassage of the fitting through the opening 9, as discernable from FIG.2. The single fitting 10 can be associated with the cap 7 detachably,adopting conventional fasteners, in such a way as to enable the filamentof interchangeable tubes 11 manufactured in different sizes withdiameters to match the various production diameters of the ends of themanifold 1, pipe 2, 4 or silencer 3 to which they must be connected andclamped at the selected points 5. Alternatively, the filtration devicemay be designed into new exhaust systems, in which case the tubes 11will coincide with and form an integral part of the manifold 1 or pipes2, 4 or silencer 3, and the flange 12 will be either integral with, orindeed replaced altogether by the cap 7.

The space encompassed by the case 6 is divided into two chambers 13 and14 of dissimilar volume by a baffle 15, disposed transversely to theaxis of the outer case 6 and made fast to it peripherally either inpermanent or removable fashion, depending on a alternative requirementsshortly to be described. 16 denotes a hollow housing, rigidly associatedwith and supported by the side of the baffle 15 directed toward thechamber 14 of greater volume, which is disposed coaxial with the case 6and remains open at the end farthest from the baffle 15. The externalsurface of the housing 16 and the internal surface of the case 6 combineto create a peripheral void 17 encircling the housing and similarly openat the end farthest from the baffle 15; the opposite end of the void 17communicates with the chamber 13 of lesser volume by way of a pluralityof openings 18 in the corresponding peripheral part of the baffle 15.

The housing 16 accommodates an axially disposed, removable filterelement 19 held in position by conventional retaining or fastening meansthat are not illustrated in FIG. 2 for simplicity's sake. The filterelement 19 is accommodated in such a way that an annular passage 20exists between its own outer surface and the inner surface of thehousing 16, thereby interconnecting the two ends of the housing. Thepassage 20 is created by expedient positioning of the filter element 19inside the housing 16, for example achieved by the incorporation ofstuds 21 designed to distance the element from the inside wall of thehousing. An alternative method (not illustrated in the interests ofsimplicity) might be to create the passage 20 by embodying the filterelement 19 with a suitably profiled outer surface, affording projectionsthat locate against the inside wall of the housing 16.

The filter element 19 is installed with one end 22 suitably perforatedand positioned at the open end of the housing 16 to take in the exhaustgases, and it opposite end 23, similarly perforated to permit expulsionof the filtered gases, breasted against the baffle 15, which constitutesthe base of the housing 16.

The drawings illustrate two alternative methods of embodying the baffle15, each designed with a given end in view (shortly to be described);whatever the geometry selected, the central area can either be leftsolid, or provided with a plurality of holes 24 evenly distributed overan area matching that of the adjacent end 23 of the filter element 19.

The embodiment illustrated in FIG. 2 assumes the use of a single filterelement 19 only; nonetheless, the option clearly exists of modifying thehousing 16 slightly to accept more than one element, arranged in such away to ensure optimum exploitation of the available space and creatingpassages 20 of varying shape, distribution and width, as in FIGS. 3a and3b, which show two possible multi-element arrangements viewed acrossA--A in FIG. 2.

In the preferred embodiment of FIG. 2, the device is embodied with acylindrical outer case 6 and filter housing 16 that exhibit circularcross section, and circular caps 7 and baffle 15, though here too, theoption exists of adopting a case 6 and housing 16, say, prismatic inshape with a quadrangular cross section as shown by way of example inFIG. 3b, or indeed of selecting other geometry and combinations that arenot illustrated in the drawings.

In effect, the geometry will be dictated ultimately by structuralfactors influencing the efficiency of the device, which are shortly tobe described. The open end of the housing 16 is positioned at a givendistance from the corresponding end of the coaxial outer case 6 and therelative cap 7, in such a way as to create a terminal void 25essentially similar to the smaller chamber 13, but no greater in volume.

To best advantage, the filter element 19 will occupy almost the totallength of the housing 16, stopping short of its projecting open end insuch a way that an intake 26 is created, serving to admit the gasesrequiring filtration and channel them into the inlet end 22 of theelement.

Finally, if the device is to operate efficiently, it is essential thatcross sectional area downstream of the peripheral void 17, i.e. thepassage afforded to the gases escaping through the baffle openings 18,be no less than that of the manifold 1 and/or the first and second pipes2 and 4.

In operation, post-combustion gases expelled through the exhaustmanifold 1 enter the terminal void 25 at normal exhaust pressure and aredirected toward the inlet end 22 of the filter element 19, assisted bythe extension of the connecting tube 11 into the void 25 and toward theintake 26, as indicated by the arrows in FIG. 2. In optimum runningconditions, the greater part of the gases will pass through the filter19, and while turbulence causes the remainder to flow directly throughthe peripheral void 17 and the baffle openings 18, a sufficiently widepassage is afforded by this route to ensure that there will be noback-pressure generated through the system. Gases filtered by theelement 19 emerge from the outlet end 23, passing through the holes 24in the center of the baffled 15 and into the smaller chamber 13 torejoin the flow through the holes 18, before leaving the deviceultimately by way of the rear fitting 10. In the event of the filter 19becoming totally blocked, gases will continue to by-pass the housingthrough the peripheral void 17, as well as flowing straight through byway of the passages 20 and the holes 24.

Where the center of the baffle 15 is solid, filtered gases leaving theoutlet end 23 of the element 19 will return toward the inlet end 22through the passages 20 and then leave the device by way of theperipheral void 17.

A device structured according to the foregoing description provides thefollowing advantages:

the passage offered to the exhausting gases remains of constant crosssectional area in any conditions, keeping losses in engine output withinthe limits specified for conventional exhaust systems;

the greater part of the gases requiring filtration find their waythrough the filter elements;

the exhaust gases are obliged to follow a tortuous route through severalchambers and changes in cross sectional area, compressing and expandingby turns; accordingly, cooling is favoured, the formation of nitrogenoxides is attenuated, and with velocity of the gases reduced, heavierpollutant solids are able to precipitate more easily.

These environmental and propulsion advantages are enhanced by thepractical bonus of a filter housing that is easily opened up andinspected simply by undoing the fasteners 8; the element 19 is thereforeeasy to replace, and the inside of the housing 16 easy to clean, albeitthe accumulation of dirt has no adverse effect whatever on engineperformance. A further advantage of the device is that the system ofchambers and passages, referred to above, brings about the deflection ofsound waves generated by the pressure loss from the flow of exhaustgases; this signifies that noise levels can also be reduced, andaccordingly, that the device will also function as a silencer. To thisend, the structure of the outer case 6 is embodied advantageously as adouble wall 61 (FIG. 4) extending substantially its entire length; inthe example illustrated, the inner wall 62 of the two is uniformlyperforated, and a layer of sound absorbent material 63 sandwichedbetween the two walls has the effect of reducing noise levels stillfurther.

Thus embodied, the filtration device disclosed can serve as a combinedexhaust silencer-and-filter, either supplementing or replacing theconventional silencer 3 in an existing system.

A further embodiment of the invention, relating to new exhaust systemsmanufactured with the filtration device built-in, and applicable oncethe geometry has been optimized to suit a given type of engine, consistsin fitting one or more of the openings 18 in the baffle 15 with shut-offmeans, or relief valves (not illustrated); such means would serve toadmit the flow of gases from the peripheral void 17 into the smallerchamber 13 only when a given level of exhaust pressure has been reachedinternally of the void 17 itself. The purpose of this expedient is toencourage passage of the gases through the filter element 19, andprovide a greater measure of control over exhaust velocity and pressure,since these are parameters that can be exploited to control velocity andpressure of the gas upstream, at the engine's exhaust valves, providingan indirect adjustment of the combustion cycle aimed at reducing theformation of pollutants during combustion.

In a preferred embodiment of the exhaust system, the filtration devicewill incorporate a substantially funnel-shaped air intake 90 associatedwith one of the axial fittings 10, arranged in such a way as to enabledilution of the exhaust gases either before or after filtration byexploiting a velocity-induced vacuum to draw clean air into the system 1from the surrounding atmosphere. Where dilution is effected prior tofiltration, as in FIG. 6a, the exhaust gases can be cooled and filteredmore efficiently; when effected post-filtration, as in FIG. 6b,particularly in systems where the filtration device is located at thetail end, the gases not only cool more quickly, but mingle with oxygenand disperse much faster.

In the preferred embodiment referred to throughout the description,inspection and servicing of the filter element 19 is permitted byremoving one of the end caps 7; with a bare minimum of modification tothe retaining and fastening arrangements however, a removable cover 30might be incorporated into one side of the outer case 6 so as to afforda lateral access point through which the filter elements 19 can beextracted, with or without their housing 16. The housing might in factbe made detachable at the baffle 15 simply by incorporating a suitablyshaped socket into the internal surface of the case 6, as illustratedschematically in FIG. 5.

The filter elements 19 might incorporate a number of different filteringmaterials layered in succession -viz, porous resin, mesh, wire wool,fabric, flock, foam, etc., dry or oil-bath, which would be selected in acombination able to trap the highest possible quantity of entrainedsolid particles and unburned hydrocarbons, compatible with an acceptableworking life.

We claim:
 1. An exhaust system for internal combustion engines providedwith a device for housing filters designed to trap solid particles andunburned hydrocarbons entrained and dissolved in exhaust gases, of thetype comprising exhaust components which include an exhaust manifold, afirst pipe, at least one silencer and a second pipe, the exhaustmanifold being connected by way of the first pipe and the silencer tothe second pipe from which the gases are ultimately exhausted, theexhaust system being suitable for use with petrol and diesel engines,comprising:a device, located at any given point along the system, havingan axially hollow outer case with open ends which are sealed tight byrigidly attached and substantially identical caps each affording anopening at a center thereof, each of said caps serving to accept arespective hermetically attached fitting by which the device itself isconnected axially to one of the exhaust components; the caseencompassing a space that is divided internally into two chambers ofdissimilar volume by a baffle that is disposed traversely and fastenedperipherally to the case, said space accommodating a hollow housingrigidly associated with and supported by the side of the baffle anddirected toward the chamber of greater volume and open at the endfarthest from the baffle, said hollow housing being disposed coaxialwith the case in such a way that an external surface of said hollowhousing and the internal surface of he case combine to create aperipheral void that is open at an end which is farther from the baffleand able to communicate at the remaining end with the chamber of lesservolume by way of a plurality of openings in a corresponding peripheralpart of the baffle, the housing accommodating at least one removablefilter element disposed axially and held in position in such a way thata passage interconnecting two ends of the housing is crated between anouter surface of the filter element and the inner surface of the housingand such that an end of the filter element designed to admit the exhaustgases is located at the open end of the housing, and another end of thefilter element from which filtered gases are expelled is breastedagainst the baffle and against the base of the housing; the open end ofthe housing being located at a given distance from the corresponding endof the coaxial outer case and the respective cap creating a terminalvoid of similar shape to the smaller chamber but no greater volume insuch a way that gases exhausted from the engine are admitted by way ofone fitting into said terminal void and expelled following filtration byway of the smaller chamber and the other fitting which is remaining; andthe total cross-sectional area offered to gases exhausting through theperipheral void and the corresponding openings in the baffle being atleast equal to that of any one of the exhaust components.
 2. An exhaustsystem as in claim 1, wherein the baffle has a central portion which hasa plurality of holes uniformly distributed over a surface area matchingthat of at least an adjacent end of said at least one filter elementaccommodated by the housing.
 3. An exhaust system as in claim 1, whereinthe one fitting has a tube insertable through the opening of arespective cap and integral with a flange that is matched to the shapeof the cap, said cap being attachable rigidly and hermetically theretoand distanced from the end of the tube in such a way that the tubeprojects a given distance into any one of the terminal void and thechamber of lesser volume when inserted through the cap.
 4. An exhaustsystem as in claim 3, wherein the tube of the one fitting exhibits across section of diameter that matches the diameter of the ends of theexhaust manifold and the first and second pipes to which they areconnected and rigidly attached.
 5. An exhaust system as in claim 3,wherein the tube of the one fitting coincides with and forms an integralpart of one of the exhaust components.
 6. An exhaust system as in claim1, wherein said at least one filter element is accommodated by thehousing in a set position established by projections issuing from saidat least one inside wall and the base of the housing in such a way as tocreate said at least one passage interconnecting the ends of thehousing.
 7. An exhaust system for as in claim 1, wherein the passageinterconnecting the ends of the housing are created by embodying theexternal surface of the filter element with projections that interactone with the other and with the inside wall and base of the housing. 8.An exhaust system as in claim 1, wherein the filter element occupiesalmost the total length of the housing, stopping short of the open endtoward the chamber in such a way that an intake is created, serving toadmit the gases requiring filtration and to channel the gases into theinlet end of the filter element.
 9. An exhaust system as in claim 1,wherein at least one of the openings in the periphery of the baffle isfitted with means for admitting the flow of gases from the peripheralvoid into the smaller chamber whenever a given level of exhaust pressureregisters through the void.
 10. An exhaust system as in claim 1, whereinthe hollow outer case of the filtration device is embodied with a doublewall structure extending substantially its entire length, comprising auniformly perforated inner wall and a layer of sound absorbent materialsandwiched between the two walls so that the case, caps and fittings,together with the housing and the filter element will also function as asilencer.
 11. An exhaust system as in claim 1, wherein the caps of thedevice are clamped rigidly to the hollow outer case by conventionalfastening means, embodied removably in order to permit of gaining accessto the housing from the outside and thus enable inspection orreplacement of the one filter element contained therein, and ofeffecting routine service and cleaning operations.
 12. An exhaust systemas in claim 1, wherein one side of the hollow outer case affords aservice cover that can be opened and tightly reshut, thus providing alateral access point through which the one filter element may beremoved, even with the housing and even without the housing forreplacement and cleaning purposes.
 13. An exhaust system as in claim 1,wherein the filtration device is embodied with said cylindrical outercase, and accordingly, with said caps and said baffle that are circularwhen seen in plan.
 14. An exhaust system as in claim 1, wherein thehousing of the filtration device is cylindrical and exhibits a circularcross section.
 15. An exhaust system for as in claim 1, wherein thefiltration device comprises an air intake associated with one of thefittings and arranged in such a way as to enable dilution of the exhaustgases by exploiting the vacuum generated in the wake of the exhaustinggases to draw air into the system from the surrounding atmosphere. 16.An exhaust system as in claim 15, wherein the air intake is arranged toenable dilution of the gases before filtration.
 17. An exhaust system asin claim 15, wherein the air intake is arranged to enable dilution ofthe gases after filtration.